My brother-in-law sometimes works as a umpire for college baseball games out in California. Umpires have a tough job and they have to keep their eyes peeled (like geocachers). Sometimes they get in to heated discussions with players and managers. Usually it's about whether someone is safe or is out. The important thing is that the umpire needs to make a decision even if they are on the fence. You are looking for a small bison.
This is located at the Floyd Hull Stadium and the Morton Activity Center. The park was home for the Big League World Series (a baseball tournament featuring players between 16 to 18 year olds) for 29 years before it was moved. Floyd Hull was part of Little League baseball for 40 years. This park has, you guessed it, baseball fields that are still being used today. The park hours are from 8 AM until 9 PM but you can access the cache at any time.